Showing papers on "Dehydroascorbic acid published in 2009"

Vitamin C: update on physiology and pharmacology

Abstract: Although ascorbic acid is an important water-soluble antioxidant and enzyme cofactor in plants and animals, humans and some other species do not synthesize ascorbate due to the lack of the enzyme catalyzing the final step of the biosynthetic pathway, and for them it has become a vitamin. This review focuses on the role of ascorbate in various hydroxylation reactions and in the redox homeostasis of subcellular compartments including mitochondria and endoplasmic reticulum. Recently discovered functions of ascorbate in nucleic acid and histone dealkylation and proteoglycan deglycanation are also summarized. These new findings might delineate a role for ascorbate in the modulation of both pro- and anti-carcinogenic mechanisms. Recent advances and perspectives in therapeutic applications are also reviewed. On the basis of new and earlier observations, the advantages of the lost ability to synthesize ascorbate are pondered. The increasing knowledge of the functions of ascorbate and of its molecular sites of action can mechanistically substantiate a place for ascorbate in the treatment of various diseases.

Vitamin C and the role of citrus juices as functional food.

Abstract: The literature on the content and stability of vitamin C (ascorbic acid, AA) in citrus juices in relation to industrial practices is reviewed. The role of vitamin C from citrus juices in human diet is also reviewed. Citrus fruits and juices are rich in several types of bioactive compounds. Their antioxidant activity and related benefits derive not only from vitamin C but also from other phytochemicals, mainly flavonoids. During juice processing, temperature and oxygen are the main factors responsible for vitamin C losses. Non-thermal processed juices retain higher levels of vitamin C, but economic factors apparently delay the use of such methods in the citrus industry. Regarding packing material, vitamin C in fruit juice is quite stable when stored in metal or glass containers, whereas juice stored in plastic bottles has a much shorter shelf-life. The limiting step for vitamin C absorption in humans is transcellular active transport across the intestinal wall where AA may be oxidized to dehydroascorbic acid (DHAA), which is easily transported across the cell membrane and immediately reduced back to AA by two major pathways. AA bioavailability in the presence of flavonoids has yielded controversial results. Whereas flavonoids seem to inhibit intestinal absorption of AA, some studies have shown that AA in citrus extract was more available than synthetic ascorbic acid alone. DHAA is reported to possess equivalent biological activity to AA, so recent studies often consider the vitamin C activity in the diet as the sum of AA plus DHAA. However, this claimed equivalence should be carefully reexamined. Humans are one of the few species lacking the enzyme (L-gulonolactone oxidase, GLO) to convert glucose to vitamin C. It has been suggested that this is due to a mutation that provided a survival advantage to early primates, since GLO produces toxic H2O2. Furthermore, the high concentration of AA (and DHAA) in neural tissues could have been the key factor that caused primates (vertebrates with relative big brain) to lose the capacity to synthesize vitamin C. Oxidative damage has many pathological implications in human health, and AA may play a central role in maintaining the metabolic antioxidant response. The abundance of citrus juices in the Mediterranean diet may provide the main dietary source for natural vitamin C.

Optimization of methodology to analyze ascorbic and dehydroascorbic acid in vegetables

Abstract: In this study, different solutions to extract vitamin C were tested. High-performance liquid chromatography was chosen and the conditions were based on isocratic elution in reverse phase column. Dehydroascorbic acid was determined indirectly after its reduction using dithiothreitol. The use of metaphosphoric acid to stabilize the vitamin C was shown to be required and it was necessary to neutralize the pH of the extract to apply dithiothreitol. The average recovery was 90% in collard and tomato samples. The presence of oil did not interfere in extraction and the methodology can be used to analyze stir fried vegetables.

The combination of vitamin D3 and dehydroascorbic acid administration attenuates brain damage in focal ischemia

Abstract: The aim of this study is to determine the protective effects of vitamin D3 and dehydroascorbic acid (DHA), a blood-brain barrier transportable form of vitamin C, against ischemia/reperfusion (I/R) injury on a middle cerebral artery occlusion/reperfusion model of brain since reactive oxygen species play an important role in the pathophysiology of I/R injury in brain. In order to examine antioxidant status and lipid peroxidation, we assayed malondialdehyde (MDA) levels as a marker of lipid peroxidation, and reduced glutathione (GSH) and superoxide dismutase (SOD) enzyme activities as free radical scavenging enzymes in cortex and corpus striatum (CS). Wistar albino rats were divided into five equal groups of each consisting of seven rats: control, I/R, I/R + DHA, I/R + vitamin D3, and I/R + vitamin D3 + dehydroascorbic acid groups. MDA levels were found to be increased in the I/R group, I/R + DHA, and I/R + vitamin D3 groups compared with the control group in both cortex and corpus striatum. However, MDA level were found to be significantly decreased in only I/R + vitamin D3 + DHA group compared with the I/R group in cortex (P < 0.0001). MDA levels were not significantly different in I/R + DHA, and I/R + vitamin D3 groups compared with the I/R group. GSH and SOD enzyme activities were significantly decreased in I/R, I/R + DHA, and I/R + vitamin D3 groups compared with the control group in both cortex and corpus striatum (CS) (P < 0.0001). Whereas, both GSH and SOD activity were increased in I/R + vitamin D3 + DHA group compared with the I/R group in both cortex and CS (P < 0.001 in cortex, P < 0.001 in CS for SOD P < 0.002 in cortex P < 0.03 in CS for GSH). Our results demonstrate that the combination of vitamin D3 and DHA treatment prevent free radical production and dietary supplementation of vitamin D3 and DHA which may be useful in the ischemic cerebral vascular diseases.

Folic acid or combination of folic acid and vitamin B12 prevents short-term arsenic trioxide-induced systemic and mitochondrial dysfunction and DNA damage

Abstract: The effect of folic acid and folic acid + vitamin B(12) supplementation upon short-term arsenic-induced systemic and pancreatic islet cell mitochondria oxidative stress was investigated in male rats. Arsenic trioxide was administered orally at a dose of 3 mg kg body weight(-1) day(-1) for 30 days, and folic acid and vitamin B(12) were administered at a dose of 36 and 0.63 microg kg body weight(-1) day(-1), respectively, for 30 days. Compared to control, arsenic-treated group showed a significant increase in the levels of systemic oxidative markers, malondialdehyde (MDA), nitric oxide (NO), and hydroxyl radical (OH(-)) formation, which were found decreased significantly after supplementation either with folic acid or a combination of folic acid + vitamin B(12). Similar supplementations were found effective against arsenic-induced oxidative marker changes (MDA, NO, and OH(-)) in pancreatic islet cell mitochondria. Also, low activities of antioxidant defense enzymes such as superoxide dismutase and catalase, and level of antioxidant glutathione, all could regain significantly on supplementations both against systemic and islet cell mitochondria oxidative stress. Results of agarose-gel electrophoresis of DNA from lymphocytes and islet cells of arsenic-exposed rats showed DNA smearing, which could be reduced with simultaneous administration either with folic acid or a combination of folic acid + vitamin B(12). Significantly, similar supplementations were found effective in increasing the urinary clearance of arsenic. Together, these results indicate that folic acid and vitamin B(12) may be effective to reduce the arsenic-induced damage at molecular target level.

The effects of washing treatment on antioxidant retention in ready‐to‐use iceberg lettuce

Abstract: Summary The influence of washing treatment on the retention of key antioxidants in minimally processed iceberg lettuce was examined. Shredded iceberg lettuce was subjected to one of three washing treatments: a domestic wash (tap-rinsed), immersion in distilled water (water-dipped) or immersion in chlorinated water (chlorine-dipped). Lettuce was subsequently packed in oriented polypropylene bags and flushed with 100% nitrogen and stored at 4 °C. Vitamin C (ascorbic acid and dehydroascorbic acid), total phenols, total antioxidants, individual phenols, individual carotenoids, colour measurements and pH were quantified on production day and throughout the storage period (8 days). Different groups of antioxidants were found to differ in their response to washing treatments. No significant (P > 0.05) effects of washing treatment were observed on total antioxidant activity, total phenolics and on the levels of individual phenolics (chicoric acid, chlorogenic acid and caffeic acid). Individual carotenoids were initially affected by washing treatment, with higher levels of lutein and beta-carotene retained with domestic washed lettuce. Ascorbic acid was the antioxidant most affected by washing treatments with domestic washing resulting in significantly (P ≤ 0.05) higher retention of ascorbic acid throughout the storage period compared with the chlorine-dipped lettuce.

Uptake of ascorbic acid by human neutrophils.

Abstract: Human neutrophils produce bacterial oxidants that could have a damaging effect on the neutrophils themselves. For protection, neutrophils acquire a high (10–20 mmol/L) level of intracellular ascorbic acid by oxidizing extracellular ascorbic acid to dehydroascorbic acid, rapidly taking up the dehydroascorbic acid and re-reducing it to ascorbic acid.

Avaliação dos efeitos da radiação gama nos teores de carotenóides, ácido ascórbico e açúcares do futo buriti do brejo (Mauritia flexuosa L.)

Abstract: Buriti (Mauritia flexuosa L.), a typical fruit from the Northeast and Center-West Amazon of Brazil, is used in many regional dishes. It is considered an excellent source of carotenoids that are A vitamin precursors, showing a majority of β-carotene. It also presents ascorbic acid and sugar contents. Many studies have indicated that the lack of A vitamin is the main cause of night blindness and xerophthalmia. Also, ascorbic acid deficiency may cause scorbutic disease. The use of food irradiation is growing and represents an economic benefit to agriculture through the reduction of post-harvesting losses while maintaining food nutritional quality. In this study, Buriti in natura was treated with gamma irradiation with doses of 0.5 kGy and 1.0 kGy. The objective was to evaluate the irradiation effects on total carotenoids, ascorbic acid and sugars concentrations of Buriti. The fruit was evaluated through the total carotenoids analysis, by spectrophotometry, and the carotenoids (α and β-carotene and lutein), ascorbic acid and sugars were determined by High Performance Liquid Chromatography (HPLC). The results showed that buriti is an excellent source of total carotenoids (44600 μg/100g). The irradiation of buriti with the dose of 0.5 kGy did not significantly change carotenoids and sugars contents. However, there was a reduction of ascorbic acid concentration with an increase of the dose, which may have been caused by irradiation or by intrinsic and extrinsic factors that alter ascorbic acid stability in food, converting ascorbic to dehydroascorbic acid, while keeping the C vitamin active form.

Rapid determination of ascorbic acid, dehydroascorbic acid, and total vitamin C by electrochemiluminescence with a thin-layer electrochemical cell

Abstract: This paper reports on a rapid and sensitive method for the simultaneous determination of ascorbic acid (H2A), dehydroascorbic acid (DHA), and total vitamin C by electrochemiluminescence (ECL) using a thin-layer electrochemical cell. Significant ECL signals can be generated by the anodic oxidation of Ru(bpy)32+ in the presence of H2A or DHA in pH 8.8 phosphate buffer solution. Because of the extremely small dead volume of the thin-layer cell (approximately 1.5 μL), almost all amount of H2A is assumed to be completely oxidized to DHA with a short pre-electrolysis step. As a result, it is possible to determine the reductive vitamin C (H2A) by square wave voltammetry before the pre-electrolysis step, while total vitamin C (sum of H2A and DHA) is able to be determined at a subsequent ECL step. The method was employed for the determination of vitamin C in commercial beverages with the analytical results in good agreement with the certified values.

Dynamic aspects of ascorbic acid metabolism in the circulation: analysis by ascorbate oxidase with a prolonged in vivo half-life.

Abstract: Because AA ( L -ascorbic acid) scavenges various types of free radicals to form MDAA (monodehydroascorbic acid) and DAA (dehydroascorbic acid), its regeneration from the oxidized metabolites is critically important for humans and other animals that lack the ability to synthesize this antioxidant. To study the dynamic aspects of AA metabolism in the circulation, a long acting AOase (ascorbate oxidase) derivative was synthesized by covalently linking PEG [poly(ethylene glycol)] to the enzyme. Fairly low concentrations of the modified enzyme (PEG―AOase) rapidly decreased AA levels in isolated fresh plasma and blood samples with a concomitant increase in their levels of MDAA and DAA. In contrast, relatively high doses of PEG―AOase were required to decrease the circulating plasma AA levels of both normal rats and ODS (osteogenic disorder Shionogi) rats that lack the ability to synthesize AA. Administration of 50 units of PEG―AOase/kg of body weight rapidly decreased AA levels in plasma and the kidney without affecting the levels in other tissues, such as the liver, brain, lung, adrenal grand and skeletal muscles. PEG―AOase slightly, but significantly, decreased glutathione (GSH) levels in the liver without affecting those in other tissues. Suppression of hepatic synthesis of GSH by administration of BSO [ L -buthionin-(S,R)-sulfoximine] enhanced the PEG―AOase-induced decrease in plasma AA levels. These and other results suggest that the circulating AA is reductively regenerated from MDAA extremely rapidly and that hepatic GSH plays important roles in the regeneration of this antioxidant.

A temporal analysis of antioxidative defense responses in the phloem of Picea abies after attack by Ips typographus.

Abstract: Summary The temporal gradation of antioxidants was investigated on the phloem tissue of Norway spruce [Picea abies (L.) Karst.] in response to weather conditions and colonization levels of Ips typographus L. (Col., Scolytidae). Two weeks after pheromone dispensers were placed on trees, the initial reaction of Norway spruce to bark beetle attack resulted in moderately lowered levels of total glutathione (tGSH) and total cysteine. Likewise, the total ascorbic acid dropped slightly below the control levels, whereas the concentration of dehydroascorbic acid increased in comparison to the first sampling date. This transient degradation and oxidation of glutathione and ascorbate system was accompanied by moderately increased concentrations of total phenolics. One month later, the shift in antioxidant balance after moderate attack differed quantitatively from the reaction after massive attack. An intensification of antioxidant defense occurred within moderately affected bark. Total cysteine and tGSH contents were markedly raised, whereas the concentrations of total ascorbic acid and total phenolics were slightly increased by moderate attack. On the other hand, massive bark beetle colonization caused a strong decrease in tGSH and total phenolics, whereas total cysteine and total ascorbic acid values remained at control level. Dependent upon the intensity and the success of the attack, a progressive degradation of antioxidants was determined at later sampling dates, which was accompanied by an obvious oxidation of the ascorbate and glutathione pools. With an unsuccessful defense upon massive attack, the thiols and total phenolics did not reach a new steady state, but deteriorated until the end of the brood beetles’ development. In contrast, the dynamic antioxidative response within the moderately affected trees indicated an acclimation stage in the middle of July. It was characterized by a higher accumulation of tGSH, total ascorbic acid and total phenolics as well as a more reduced redox state of glutathione. A sequence of changes in the endogenous levels of antioxidant defense molecules in the bark beetleaffected Norway spruce showed consistency with the general ecophysiological stress–response concept, and provided important avenues for evaluating the role and effectiveness of antioxidants in systemic acquired resistance against the complex interactive effects of bark beetle attack and environmental factors.

The mechanism of uptake of ascorbic acid into osteoblasts and leukocytes.

Abstract: Ascorbic acid is taken up into osteoblast cells by a saturable, stereospecific, Na+-dependent transporter, accumulating ascorbic acid to a level 100-fold that in the medium. The ascorbic acid uptake rate correlated with intracellular hydroxyproline synthesis. A second, distinct mechanism has also been described for accumulation of ascorbic acid into neutrophils and myeloid leukemia cells. This appears to be Na+-independent and relies on the glucose transporter GLUT1 to ferry dehydroascorbic acid (DHA) into cells and then to trap it as ascorbic acid to a high concentration.

Comment re: Vitamin C antagonizes the cytotoxic effects of chemotherapy.

Abstract: To the Editor: On the basis of cell and animal experiments with dehydroascorbic acid, Heaney and colleagues state, “These results suggest that supplementary vitamin C may have adverse consequences in patients receiving cancer therapy” ([1][1]). Selectively referring to dehydroascorbic acid as

Kinetic properties of dehydroascorbic acid transport in erythrocytes of young and adult beagle dogs

Abstract: Kinetic properties of dehydroascorbic acid (DHA) transport were studied in erythrocytes of beagle dogs at 1 and 12 months. DHA uptake was much faster in erythrocytes of dogs at 1 than 12 months. Young dogs showed much greater affinity for DHA than adult dogs and the rate of DHA uptake was not affected by glucose. It was due to the presence of fetal erythrocytes with high activity of Glut-1 glucose transporter in young dogs. In adult dogs, DHA uptake was slow and competitively inhibited by physiological concentrations of glucose. Glut-4 was identified as the carrier protein responsible for DHA uptake in erythrocytes of adult dogs. Glut-4 was hardly detectable in neonatal dogs, but increased to adult levels by 3 months as fetal erythrocytes were eliminated and switched to adult cells.

Inhibition of apoptosis by ascorbic and dehydroascorbic acids in Xenopus egg extracts.

Abstract: Purpose The viability of mammalian eggs after ovulation is reported to be improved by the presence of ascorbic acid in the culture medium. However, the pro-survival mechanisms of ascorbic acid are poorly understood. The molecular pathways of apoptosis are evolutionarily conserved among animal species, and Xenopus eggs are technically and ethically more suitable for biochemical analyses than mammalian eggs. We used Xenopus egg cytoplasmic extracts to examine the direct intracellular effects of ascorbic acid.

Molecular bases of the cellular handling of vitamin C transport and metabolism in health and disease.

Abstract: Under circumstances of an adequate dietary content in ascorbic acid the availability of this vitamin for cells is still not ensured. The reason could be poor intestinal absorption or impaired access to cells in different tissues because, owing to the marked hydrophylicity of this molecule, the rate of free diffusion across plasma membranes is low. Indeed the role of carrier proteins in vitamin C uptake has been recently recognized. This was formerly believed to occur via passive transport, in which sugar carriers belonging to the GLUT family were assumed to be involved. However, more recently it has been described that ascorbic acid absorption by the intestine and uptake by cells from the blood requires more specific plasma membrane transporters for vitamin C as a substrate and with the higher efficiency that is characteristic of active systems. In this case, the energy for active vitamin C uptake is provided by inwardly directed sodium gradients. The differential tissue distribution of isoforms 1 and 2 of sodium-dependent vitamin C transporters (SVCT) accounts for the general and specific functions of these proteins in anti-oxidant systems responsible for cell homeostasis or more cell-specific roles in which vitamin C is involved, such as trans-epithelial transfer or collagen synthesis. Changes in the expression of these transporters in association with oxidative stress and inflammation have been described. In the present review, their role in physiology and in both the aetiology and pathogenesis of several diseases is discussed. © 2009 by Nova Science Publishers, Inc. All rights reserved.

Preparation method for high-purity solid dehydroascorbic acid

Abstract: The invention relates to a preparation method for high-purity solid dehydroascorbic acid, which is obtained by the following steps: 1. oxidizing L-vitamin C (Vc); 2. removing active carbon and lower alcohol solvent; and 3. refining the dehydroascorbic acid. Compared with the previous method, the invention adopts the high efficiency liquid chromatography to analyze and monitor the process of oxidizing L-vitamin C so as to ensure the thorough reaction of the L-vitamin C, and adopts the column chromatography to refine the dehydroascorbic acid. The method has the advantages of simple process, easy control, safety without toxic substance and no environmental pollution. The analysis of the high efficiency liquid chromatography indicates that the content of dehydroascorbic acid in the solid prepared by the preparation method is up to more than 95% by using the area normalization method.

Hplc-電気化学検出法による野菜・果物中のビタミンcの定量に関する検討

Abstract: The content of vitamin C in 17 kinds of vegetables and fruits was analyzed by two different high-performance liquid chromatographic (HPLC) methods, one with electrochemical detection (HPLC-ECD), and the other with visible absorption detection (hydrazine/HPLC-VIS). The data and usability were compared between these two methods. The value for total vitamin C (ascorbic acid+dehydroascorbic acid) by HPLC-ECD was comparable to that by hydrazine/HPLC-VIS, and significant correlation was obtained (r=0.984, p<0.01). When compared to the hydrazine/HPLC-VIS method, HPLC-ECD required fewer steps for the analysis and a shorter analytical time, gave a higher specificity for ascorbic acid, and could be applied for the analysis of both ascorbic acid and dehydroascorbic acid. These results show the superiority of the HPLC-ECD method for a vitamin C analysis of vegetables and fruits.

Vitamin C and Lycopene Contents in Different Parts of Seedless Watermelon Fruit

Abstract: To investigate Vitamin C and lycopene contents in different parts of watermelons fruit,7 triploid seedless watermelon cultivars,including 6 red and 1 yellow flesh,were sampled to determine their total ascorbic acid(TAA),ascorbic acid(AA),dehydroascorbic acid(DHAA) and lycopene contents.TAA,AA,DHAA and lycopene contents of 3 uncut red flesh seedless watermelon cultivars were measured after storage at room temperature for 2 months.The results showed that TAA,AA,DHAA and lycopene contents significantly differ among cultivars and at different parts of watermelon fruits.TAA,AA,DHAA and lycopene contents in heart portion were higher than those of near rind.The correlation between TAA,DHAA and lycopene contents was significant(P0.01);the correlation between AA and DHAA contents was significant at P0.05 level.The losses of TAA,AA,DHAA and lycopene contents were different among uncut seedless watermelons after 2 month storage at room temperature,and the losses were 20%-50%.

Effect of ascorbic acid, diketogulonic acid and dehydroascorbic acid on bovine serum albumin on storage in the glassy state *

Abstract: Showing the occurrence of glass/rubber transition in bovine serum albumin (a globular protein) at low moisture levels and the occurrence of Maillard crosslinking in gelatin in previous works, the importance of the state of glass or rubber of BSA on the rate and extent of polymerisation, protein solubility, colour and SDS PAGE patterns in the presence and absence of ascorbic acid, diketogulonic acid and dehydroascorbic acid was investigated. BSA on storage with Ascorbic acid and its degradation products at low moisture contents (8.3% and 19.1%) at a relatively low temperature (40oC) can undergo chemical changes resulting in marked increase in molecular weight, solubility decrease and formation of browning colour. The glassy state data established the occurrence of chemical changes (Maillard crosslinking and disulfide crosslinking) in the BSA system on storage below its glass transition temperature.